Fluid heating unit



June 24, 1958 E. DURHAM 2,840,049

' FLUID HEATING UNIT Filed May 20, 1954 I 3 Sheets-Sheet l INVENTOR ATTORNEY June 24, 1958 E. DURHAM FLUID HEATING UNIT 3 Sheets-Sheet 2 Filed May 20, 1954 ATTORNEY INVENTOR fdn m Durham June 24, 1958- E. DURHAM FLUID HEATING UNIT 3 Sheetshe et 3 Filed May 20, 1954 INVENTOR Edwin Dar/1am BY ATTORNEY Application May 20, "1954, Serial No. 431,123

7 Claims. (Cl., 122--=333) This inv ention 'relat'es'in gen'eral'to the construction of 'fluid heating units particularly adapted and especially useful for furnace 'operation under superatmospheric pressures. More particularly, the invention is directed tothe coiis'truetion of fluid heating units of the character described having an elongated setting of circulated cross- "section including an elongated furnacechamber of circul'ar cross-"section in communication with a lateral gas pass in which arepositione'd fluid heating'tubes.

In recent years there has been a trend towards the superatmospheric pressure combustion of fuels. These '(conibustionfpressures have ranged from 1 p: s. i. to over 100 p. s. i. Positive gas'presgure in fluid heating units have created many mechanical design difficulties when the heatinggas is confined in; essentially rectangular set tings of penile ional fluid heaters. I g H H The large walls of these rectangular units must be reinforcedw th heavy structural members in order to withstand the positive pressures. From a mechanical standpoint, a rectangularcross-section is inherently not adaptedfo'r the use of minimum size structural parts. Therefore,,superatmospheric pressure gas units of this type havebecome more complicated and expensive with increases heating, capacityand combustion presfsure. fIt haspbecoine inbreasinglyapparem that there is an ecohorniclirhit of fdesign pressures for rectangular 1 units.

ngs riaeeana pressure ohtaining walls e'ou'sfy air i'cable f gh heatih g gas TheYadapthtion of this type of unit 1t o f the new nearing sure ossible ibyf utilizing pressure-carryrme'd n acynadricai shape, which g anyparticularpressure with a 1 1- xinruni efficiency-o mh'ter'ial utirization.

More 'spcifically, this "invention rovides an arrangement of fluid heatihg"sfirface within a vertically elonrgated 'sett'ing "of circularr cross section including a 'verti'cally elongatedifurnace chamber of circular crossse'ct-ion within saidsetting; a jlateral convection heating water; cooled antiwar "and tax ii'r'ciinifereniially en- "-closih-'g"= the furnace chamber bfthe unit to provide a plenuht-tcliamber foricombustionrair. f

Another feature of this invention is the provision of a Ahbther of this nternist n ne roii iea or I Unifiid statis a ent. 0"

. 2 4 0 9 bath-tea June '24, 1958 fluid heating unit of'the type described which is capable of burning a low heating value fuel in conjunction with a high heating value fuel in the furnace thereof and having a fluid cooled annular type wind box circumferentially enclosing the furnace chamber which is segmentally divided int o chambers, some of which are for combustion air and gaseous fuel. t J

The various features of novelty whichcharacterlze the others for a low heating value the invention are pointed outwith particularity in theclaims annexed to and "forming a part of this specifica tion. For a better understanding of the invention, its

operating advantages and specific objects attained by its use, reference should'be had to the accompanying drawings and descriptive matter in 'whichI have illustrated and described apreferred embodiment of myin'vention.

0f the drawings: 7

Fig. 1 is a vertical section "of a pressure-fired steam generating unit constructed according to the invention;

Figs. 2, 3, and 4 are horizontal sections taken on the lines 22, 33, and 4l4 respectively of Fig. 1; I

Fig. 5 is a fragmentary enlarged view of the setting shown in Fig. 2 at positionA; and

Fig. 6 is a vertical section taken on the line 6--6 of Fig. :5.

The steam generating unit illustrated in the drawings is composed of a'vertically elongated setting of a circular cross-section throughout its height. The setting includes an elongated furnace chamber ltl'of a circular cross-section in the lower part of the setting and a lateral heating gas pass 12 in communication with the furnace chamber 10 in the upper part of the setting. The furnace chamber is defined by cylindrical wall portions 14, 14B, circular refractory floor 16, and a wing bathe 18. The baflie 18 cooperates with the upper circular setting wall portion 14A and roof 20 to form the lateral convection gas pass 12. A steam and water drum '22 is arranged to extend along the transverse centerline of the top of the setting and directly below, across the bottom the gas. pass 12, is'an elongated water drum 24 with banks of upright steam generating tubes 26 connected between the drums. A'steam'superheater 25 is disposed in the pass 12 ahead of the tube banks 26.

In the lower end of the setting there is a toroidal distributingheader 23 which receives water from downcomers 30. Leading upwardly from the toroidal header 28 are wall tubes 32 arranged in a circular pattern. These tubes define the furnace chamber wall portions 14, 14B

and the convection gas pass defining wall portion 14A and are connected to an upper toroidal header 36.. Also leading upwardly from the lower header 28 in spaced relationship throughout approximately three quarters of the periphery of the setting are tubes 38 which are first directed radially outwardly and are then bent upwardly parallel to the furnace wall along the outer circular wall 43 of an annular wind box 40. The tubes are then bent radially inwardly passing through the furnace wall and Y forming in conjunction with refractory an orifice type bafile 42. 'The tubes 38 are then bent back into the plane of the wall portion 148 and continu'e'up to the upper toroidal header 36.

InFig. 3 there is more clearly shown the tube pattern of the orifice baffle 42 showing how the tubes ss'a're bent inwardly out of the plane of the outer wall 43 the annular wind box 40, through the furnace wall portion 14 and thence back into the wall portion14B, wherein the steam generating tubes are in tangent relationship .to each other and form a tube to tube circular pattern.

The roof tubes 45 are risers carrying a vapor-liquid mixture from the upper header 36 to the drum 22. .Separately connected to the downcomer 30 is a segmental the tubes 46 are then connected to the lower drum 24.

In Fig. .2 there is more particularly shown the tube pattern of thewing baflie 18 wherein the tubes 46 bend out of the plane of the wall of the setting in substantially parallel relationship before turning in and being attached to the lower drum 24. There is also shown the tube pattern of the fluid heating tube bank 26, the tubes of which connect 'the drums 22 and 24. This figure also shows thetubes are inan aligned relationship, filling the entrretran sverse widthofthe lateral gas passfi12.

In addition ythere is shown the aligned tube pattern of the superheater 25 which'is disposed gas flow-wise ahead of the generating bank 26.

The entirecircular setting and, steam, pressure parts are top supported from the structural steel 48 by upper drum U-bolts 50, thus the thermal expansion of the setting is downward, Also hung from the steel work 48 is the pendent type superheater 25 which is composed of a plurality of tubes which are sinuously bent to form a .tube'bank extending across the entire width of the lateral gas pass 12.

To prevent gas by-pass around the tube bank 26 the roof tubes 45 cooperate with. refractory to form a gas-tight closurethus defining the roof 20 of the lateral gas pass ing a regeneration of a catalyst used in a hydrocarbon cracking process- .The low heating value gas. is composed of carbon dioxide, carbon. monoxide, nitrogen, oxygen, water vapor and hydrocarbon .vapor. The carbon monoxide and hydrocarbon vapors lcan be oxidized to CO and H .in. an exothermic .processby the. addition of an oxidizing medium suchlas air with a release of about The amount of heat released is small and is not sufficient tomaintain combustionwhen mixed with relatively cool air but if a furnace temperature of approximately 1500." For higher is maintained the gas will -burnin theprcsence of air. As large amounts of this gas are discharged from. a ca'talystic cracking unit it is desirable.in the interest of an eflicient cracking process to utilize the. heat from these .gases. Accordingly, in this invention the gas isburnedin' a combustion atmosphere .of high heatingvalue fueloil and air wherein the com.- bustion temperature is in excess of' 1500 F. 'Ashereinafter described the low heating value gas and high heating value fuel'are separately introduced into the furnace 10 in a manner-for etficient heat release. Afterward, the products of combustion are passed through the setting of a fluid for the generation and superheating of steam.

The furnace .10 is ,1 divided into a lower'combustion .zone .54 and an upper radiation zone 56 by the orifice type batfle ,42.- Disposed in the fluid cooled wind box, and passing through the. wall portion 14 of the furnace 10 there is a plurality of high heating value fuelburners 58 taining four burners and each burner having its centerline tangent toanimaginary circle 5 9 (Fig. 4), which circle preferably has iftslcenter onthel'on'gitudinal axis of the furnace 10.. Combustionf airis furnished to the burners from anair duct :6Qfthe1 air beingdischargedto a plenum chamberf 62 below thefloor 16. This plenum chamber is formed b y a lower-circular casing 64'anda downward extension66 of the vertical side wall 43. 'Theair is fluid heating tubes 32 and flows'upwardly into tlie fluid cooled wind box 40. The wind box 40 is segmentally divided by the longitudinal baflles 68 so that, for example, secondary air for the burners 58 passes into wind box segments, or segmental chambers 70 formed between successive bafflcs 68.

arranged in vertically spaced rows with eachrow con- Arranged in the wall portion 14 of the furnace combustion zone 54 are two rows of low heating value gas ports 72 which are vertically spaced at alternate levels below the high heating value burners 58. Each row contains eight gas, ports with each port 72 being circumferentially spaced from the position of the high heating value burners 58 and with the ports having their longitudinal centerlines tangent to an imaginary circle 74 concentric with the longitudinal axis of the furnace. This latter circle being concentric with the tangent circle 59 of the high heat value burners but having a greater radius. Furthermore, the tangential gas port rows are spaced vertically from the high heating value fuel burner rows. The low heating-value gas enters an extension 40A of the annular wind box 40 from the supply duct 71 and, by virtue of the segmental division of the annular wind .box by thebaflles 68, flows downwardly in the gas chambers -75 and thence through the ports 72. The combustion air for the gas will normally be obtained from the excess air introduced through the high heat value burners 58 but by opening dampers 78, air from the air chambers will mix with the gas before going into the furnace 10.

The wall portion 14 of the combustion zone 54 includes the steam generating tubes 32 associated with refractory, which covers the tubes andfills the spaces therebetween. This refractory covering also extends. up to and is included in the orifice baflle. 42. As can, .be seen from Fig. 4 the fluid cooled wind box 40 isiannular in shape and shares with the furnace, thecommon wall 14. Its outer circular wall 43 includes the;uprigbt parallel fluid heating tubes 38,-46. I

Throughout the entire vertical height. of the steam generating unit the setting wall is enclosedinan insulated fluid-tight casing such as illustrated in Figs. 5 and 6.

.The fluid heating tubes 32, 38 of thesetting walls are arranged upright and parallel in a circular-pattern. buckstay band, made,. for.example,'of. 1; by 3 steel bar, encompasses, in tangent relationship, all of the fluid heating tubes of the wall and is connected gby welds 84 to the tubes alternately on the top and the bqttom of the band so as to maintain the tubes in the circular pattern. These/bands 82 are placed on the tubes .at spaced vertical positions ofthe setting wall as shownin Fig. 1 so as to give support to the fluid heating tubes. IPlaced between the buckstay bands are long rectangularly shaped' thin metal casing sheets 86 which also encompass all of the fluid heating tubes in a tangent relationship. These casing sheets 86 are pulled tight against the tubes and the short edges 88 of the sheets are joined bywelding to upright butt straps 90 in such a manner that the joint is pressure tight; The long edges 92 of the casing sheet are adjacent the buck-stay. bands 82 and the. lower edges of each sheet rest on small support blocks 94 which are in turn welded to the buck-stay bands '82 Thus the casing sheets 86 are supported from the buck-stay bands without beingsecured thereto. This arrangement allows the bers 96 is also constructed of metal and is formed with its longitudinal centerline as a circle. Thus by welding'the. two ends of each channel member together and distributed radially from the plenum chamber past the by welding their flanges to the casing sheets there is comexpansion casing problems.

:pleted "a pressure-tight "ca'sin'g {structure ;:exter1 :ra1 er th'e thermal insulation 104 which, in turn, is attached to the studs 106 which are welded to the casing 86. In order to hold the lightweight thermal insulation 104 in operative position there area number of strands of wire 108 secured by the washers 110 fixedto the studs. In this example there is shown an external pr'otective insulation casing 114 which is"comp'o'sed"of thincircumfer'entially disposed metallic sheets welded to and supported by a multiplicity of spacerbars'1'12. The sp'acer'bar's in turn are welded to the pressure-tight casing sheets 86. The

protective means may alternatively include a plastic-insulation coating and in that event the externalmetallic casing and supporting means would not be required.

The fluid heater of this invention has'certain desirable characteristics. The walls are formed in a circular shape such that they will 'efliciently withstand high gas pressures of superatmospheric-pressure fired fluid heaters. This circular arrangement also provides an arrangement of fluid heating surface which makes possible the eflicient combustion of a 'widerange offluid fuels "and thesubsequent e fiicient'removal of heat from-the ensuing heating gases. Itis further to be-notedthat this general arrangement may be used with most-anycombustion gas pressure by increasing the thickness of the gas pressure casing "materials without any change 'to'thebasicfluid heating pres- :sure part arrangement.

There is -provided'a unique -fluid cooled windbox arrangement which materially reduces differential thermal Attendant with and'aninherentp'art of this fluidheater is a unique, simplified, and inexpensive fluid-tight casing which has eliminated the problems of supporting pressure walls of conventional rectangular shaped fluid heaters.

While in accordance with the provisions of the statutes I have illustrated and described herein a specific form of the invention now known to me, those skilled in the art N will understand that changes may be made in the form of the apparatus disclosed without departing from the spirit of the invention covered by my claims, and that certain features of the invention may sometimes be used to advantage without a corresponding use of the other features.

I claim: 1. In a fluid heating unit, in combination, wall means defining a vertically elongated chamber of circular cross- .section having an upper radiant zone and a lower combustion zone, means forming a heating gas outlet from said radiant zone, burner'means arranged in a plurality of vertically spaced horizontal rows for introducing streams of fuel and oxidizing medium into said combustion zone of said chamber, means forming an outer wall 'of an annular windbox circumferentially enclosing at least a substantial portion of said combustion zone of the chamber, said chamber wall means being common to said chamber and to said windbox, upright fluid heating tubes arranged in tube to tube relationship lining the wall of said radiant zone, and said annular windbox outer wall being formed in part by alternate tubes of said tube to tube arrangement being bent outwardly from said chamber wall and then directed downwardly parallel to said chamber wall.

2. In a fluid heating unit, in combination, wall means defining a vertically elongated chamber of circular crosssection having an upper radiant zone and alowercombustion' z'one, means'for'ming a heating "gasoutlet'from aid radiant izone, burner means arranged for introducing streams-of fueland oxidizingmedium into said combusranged in tube to tube relationship lining the Walls of 'said radiant'zone, means forming an outer wallof an "annular windbox circumferentially enclosing at least a be'rng' 'formed in part by alternate tubes of said tube to tube arrangement being bent outwardly from said'chamber wall and then directed 'downwardlyparallel to said chamber wall, means forming an orifice baflle transversely dividing said chamber into saidcombustion and radiation zones, said orifice bafile means being formed in part by alternate tubes of said tube to tube arrangement being bent radially inwardly from said chamber wall and then radially outwardly 'back'to said wall, and said alternate tubes formingin part both said orifice baflle and said outer'wall ofsaidfannular'windbox. I

'3. In a 'fluid heating unit, in combination, wall means defining a verticallyelongated chamber of circular cross- "section having an upper radiant zone and a lower combustion zone, rneans'forming a heating gas outlet from said radiant zone, burner means arranged in a plurality of vertically spa'ced'horizontal rows for' introducing into said combustion zone of said chamber streams of low heating valuefuelfrom alternate rows and high heating value fuel from the other of said rows, upright fiuidheatin'g tubes associated with said wall means, means forming an fouten wall of an;annular windbox circumferentially enclosing at leasta substantial portion of said'combustion zone'to the chamber, said chamber wall being common to said chamber and to said windbox, means radially dividing said a'nnul'a'r windboxinto segmental chambers, some *of the segmental 'charnbers'supplying combustion air to saidhigh heat value fuel burner, and others of the segmental chambers being arranged to supply low heat value fuel to said burn'er. I e *4/11: af-'fliiid heatingunigin combination, wall means =definifig-a ver'ti'cally elongatedcha'rnbe'r of circular'crosssection having an upper radiant zone and a lower combustion zone, means forming a heating gas outlet from said radiant zone, burner means arranged in'a plurality of vertically spaced horizontal rows for introducing into said combustion zone of said chamber streams of high heat content fuel from alternate rows and streams of low heat content fuel from the others of said rows, upright fluid heating tubes associated with said wall means;

means forming an outer wall of an annular windbox cir-, cumferentially enclosing at least a substantial portion of said combustionzone of the chamber, said chamber wall being common to said chamber and to'said windbox,

means radially dividing said annular windboxinto segmental chambers, some of the segmental chambers supplying combustion air to said high heat value fuel burner, and others of the segmental chambers being arranged to supply low heat value fuel to said low heating value burner, and damper means associated with said dividing means which upon opening introduces combustion air into said chambers of gaseous low heat value fuel.

5. In a fluid heating unit, in combination, wall means defining a vertically elongated chamber of circular crosslining the walls of said radiant zone, means forming an outer wall of an annular windbox circumferentially enclosing at least a substantial portion of said combustion zone of the chamber; saidchamber wall being jcom'rnon .to'saidchamber ndtoj said windboxrsaidannular ,vvindbojxcwall "being formed in; part: by; alternate tubes of said .tube,to,tube;arrahgernent'beirig'bent outwardly fromsaid v chamber wall and. then directed downwardly parallel, to i said chamber wall, meansgforming an orifice baffle trans- ;versely dividingsaid chamber intosaid combustion and radiation zones, said orifice haflle means being formed in partby alternate, tubes of-said tubetotube arrangement jbeing bent radially inwardly from said chamber wall and then radially outwardly; back to said wall, said alternate tubes forming in part both ,saidjorifice bafile and said outer wall of said'annular windbox,.means radially dividing said annular windbox into. segmental chambers, some of the segmental .chambers supplying combustionair to said high heat value fuel,-burner,;and others of the seg mental chambers being arranged to supply: low heat value fuelto said low heating value burner, and damper means .zones,'some of said fluid heating tubes forming in part said orifice baffle means, wing battle means extending inwardly across a major portion of said orifice opening from one side of the chamber, above and immediately adjacent said orifice battle, means defining agas outlet in a wall of said. chamber above said wing bafile means and adjacent the side of the chamber from .Which said Wing bafile means extends, and rows of fluid heating tubes extending upwardly across said convection. zone above said wing battle means whereby the heating gas flow from said combustion chamber passes upwardly at an accelerated velocity through said orifice'baflle means and is sequentially directed toward one side of said intermediate radiant zone :and,tur'ns around the. end of said .wing baffie to move in a generally horizontaldirectio'n throughsaid convection :heatingfzohej v. 1' :1. 2 ,z.

.In a: fluid heatingiunit, in'cornbination, wall means :defininga vertically elongated chamberofj substantially uniformscircularlhorizontal cross-section having an upper convection, zone, an intermediate radiant zone and a lower combustiongzone -burner means arranged at vertically spaced; positions} for, introducing. streams of fuel and oxidizingmedium into the combustion zone of said chamber, upright; fluid heatingtubes associated with said Wall means, means forming an orifice battle transversely dividing said chambeninto said combustion and radiation zones some of. said fluid heating tubes, forming in part said orificeibafiiemeans, wing baffle means extending inwardly; across a major portion of said orifice opening from one side of the chambenabove andimmediately adjacent saidorifice baffle, means defining a gas outletin a wall of said chamberabovesaid-wing battle means and adjacent the side ofthechamber from which's aidwing baffle means extends, androws of fluid heating tubes extending upwardly across said convection zone above said wing baffie means whereby the heating gas flow from said combustion chamber passes upwardly into said radiation zone at an accelerated velocity through said orifice baffie means and is sequentially directed toward one side of said radiant zone and turns around the end of said wing battle to move in a generally horizontal direction through said convection heating zone for discharge through said heating gas outlet.

References Cited in the file of this patent UNITED STATES PATENTS Belgium Dec. 15, 1952 

